1. Field of the Invention
The invention relates to and has among its objects the provision of novel processes for obtaining stable, food-grade protein concentrates from seed products, particularly seed by-products, and whey. Further objects of the invention will be evident from the following description wherein parts and percentages are by weight unless otherwise specified.
2. Description of the Prior Art
In the treatment of seed products to obtain flour, germ, peeled seeds, etc., several steps including grinding and sifting are often employed, whereby the purified product is separated from other fragments of the seed. These other fragments are by-products and include, for example, bran, shorts, and hulls. The by-products often comprise about 20-25% of the seed and contain approximately 20-25% of the protein. In addition, the by-products contain a high percentage of B-complex vitamins, such as niacin, pyridoxine, pantothenic acid, riboflavin, and thiamine. However, because of their high fiber and ash content the by-products are not suitable for human nutritional needs. The high fiber and ash content tends to accelerate the passage of the food through the human digestive tract. Consequently, only a small nutritive contribution is realized. Thus, these by-products are useful only as feed for ruminant animals, to whom the nutrients are more available.
A process for securing stable protein concentrates from millfeed is described in U.S. Pat. No. 3,859,451 (hereinafter referred to as '451) by Saunders et al. In the '451 process the millfeed is mixed with water in the ratio of about 3-5 lbs. of water per pound of millfeed. Then, alkali is added to the mixture to obtain a pH of 8 to 10. Next, a juice is separated from the solids by conventional means such as filtering the mixture through a filter cloth, centrifugation, etc. The pH of the juice is adjusted to 5.5-6.0 and steam is applied thereto to attain a temperature of 85.degree. C., whereupon the product coagulates. The coagulated protein concentrate is collected conventionally and washed.
One problem with the '451 process is that large quantities of water are required, thus increasing expenses and wasting energy, especially in drying the product. A further problem is that the protein concentrate produced, although high in protein is less than perfect for several reasons. First, the protein content could be much greater in order to satisfy increasing demands for higher-protein products. Secondly, the quality of the protein in the '451 concentrate could be improved because the balance of proteins is nutritionally inadequate as will be explained hereinbelow.
In U.S. Pat. No. 3,397,991 (hereinafter referred to as '991) a homogeneous blend of proteins derived from two or more different sources is prepared. To this end the protein sources are formed into an aqueous slurry to which is added sufficient alkali to attain a pH of 9-12. Preferably, the slurry is then heated to 66.degree.-93.degree. C. for a time necessary to solubilize the proteins. If the protein sources are solubilized individually, the solubilized proteins are combined. Following solubilization the aqueous solution of proteins is separated and treated to precipitate a protein concentrate by adjusting the cation or hydrogen ion concentration of the solution to the appropriate point. In a preferred embodiment the so-precipitated protein is neutralized and resolubilized by addition of alkali and the solution is spray-dried to yield a protein product.